Extended Reactive Power Exchange With Faulty cells in Grid tied Cascaded H-Bridge converter for Solar PhotoVoltaic Application

摘要： Fault tolerant operation is a key feature of grid tied PV fed Cascaded H-Bridge (CHB) converter, where the converter operates continuously with faulty bypassed cells. After bypassing the faulty cells, the number of healthy cells decreases, the available dc link voltage reduces and active power among the phases become unequal. As a result, the converter produces unbalanced and distorted grid currents. Moreover, the maximum reactive power exchanged with the grid gets reduced with the available DC link voltage. This paper injection proposes a novel zero sequence voltage technique for balancing the grid currents and preventing over modulation in each cell of the converter. The proposed technique extends the reactive power capability of the converter during post fault condition. Additionally, it also helps in equal active and reactive power flow in each phase of the converter. A new PWM clamping strategy is proposed in this paper to implement the zero sequence voltage addition in the converter. The proposed concept is verified through computer simulation and experimental results.